Re: Histograms

From: Jan Syssauw <jsyssauw_at_village.uunet.be>
Date: Thu, 18 Mar 1999 21:44:19 +0100
Message-ID: <7croec$jql$1@xenon.inbe.net>

Hi,

histograms on a non-indexed column: no use at all

        histograms are used to help the optimizer determine if it is of any
        interest to use the index of not (% of rows returned)
criteria: check the Oracle Tuning guide
     uneven datadistribution: for example
     column with 100 distinct values: 1 ... 100
     but 50% - 75% is a certain value: other values equally distributed

    and you have where clause referring to this column

chuckh_at_safeplace.net wrote in message <7crd46$u9d$1_at_nnrp1.dejanews.com>...
>Does anyone have a set of criteria they use to determine whether or not a
>column should have histograms on it?
>
>Is there any benefit to having histograms on a non-indexed column?
>--
>Chuck Hamilton
>chuckh_at_safeplace.net
>
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Received on Thu Mar 18 1999 - 14:44:19 CST